In the static approximation used, the evaluation of the above quantities is based on Biot-Savart's law [1]},
\(B̭(r̭) = \frac{}{4 \pi } \int \limits _\dfrac{J̭(r̭^{\prime }) \times \left(r̭ - r̭^{\prime }\right)}{|r̭ - r̭^{\prime }|^3} V̥^{\prime },\) 
